An illuminator, audiovisual equipment, an electronic apparatus, mobile computing devices, a liquid crystal television, a plasma display, and the like have functions of making the surroundings bright, transmitting a light signal, projecting an optical image or the like, by emitting visible rays. Some of these apparatus have a light reflector and improve the luminance of light or change the direction of light by reflecting light on the reflector. Therefore, in order to avoid a drop in the quantity of light when light is reflected by a reflector, the surface of the reflector requires a high visible ray reflectance. As means for improving the reflectance of the surface of a reflector in the past, for example, a metal has been polished to make a mirror plane, or a white coating material with a high reflectance has been coated. Nippon Steel Corporation catalog “View coat” discloses a precoated steel sheet coated with a white coating material beforehand for light reflectors of an illuminator.
Japanese Unexamined Patent Publication No. Hei 10-000730 discloses a light reflecting film excellent as a light reflector for a liquid crystal display, comprising a substrate film, a thin metal film layer laminated on one side of the substrate film, and a fine inorganic particle-containing resin layer laminated on the thin metal film layer, wherein the thin metal film layer is made of aluminum, and the reflective indices nf and nb satisfy the relationship nf−nb>=0.4 in which nf is the refractive index of the fine inorganic particle and nb is the refractive index of the resin. Japanese Unexamined Patent Publication No. 2002-172735 discloses a highly diffusing reflective coated metal panel used as a reflecting plate for the back light of a liquid crystal display, comprising an aluminum panel, an undercoat layer formed on the aluminum panel, and a topcoat layer formed on the undercoat layer, wherein the undercoat layer contains 100 parts by weight of a resin and 150 to 300 parts by weight of a titanium oxide pigment and has a film thickness of 50 to 100 micrometers, and the topcoat layer contains 100 parts by weight of a resin and 100 to 250 parts by weight of a titanium oxide pigment and has a gloss of not more than 15 and a film thickness of 10 to 30 micrometers. However, the need of forming a light reflector used for an illuminator and for an electric apparatus, such as a liquid crystal display, into various shapes before use has been increasing with complication of the structure and design of an electric apparatus in recent years.
However, when a film is used as a substrate as described in Japanese Unexamined Patent Publication No. Hei 10-000730, it is difficult to form a film, laminated with a metal thin film layer or a resin layer containing fine inorganic particles beforehand, into a target shape. Therefore, the film must be formed into the target shape in advance before laminating the metal thin film layer or the resin layer containing fine inorganic particles. However, when a shape of a light reflector is complicated, it is difficult to laminate a coat, on the formed part, with a uniform thickness.
On the other hand, according to the technique described in Japanese Unexamined Patent Publication No. 2002-172735, after applying an undercoat layer and a topcoat layer to an aluminum plate beforehand, the coated aluminum plate can be formed into a target shape. However, as the amount of titanium oxide added in a reflective coat was too high, the coat was weak, and there were problems that cracks occurred in the reflective coat or the coat peeled at the time of forming. Moreover, it also has a weak point that formed shapes are limited because aluminum, which is a base metal, has a poor forming workability. Furthermore, it is very difficult to coat an undercoat with such a thickness (50 to 100 micrometers) at one time by a roll coater on a common precoating line, and it is necessary to coat two or more times, and therefore there is a weak point of low productivity.
Consequently, it was difficult to apply the light reflector described in Japanese Unexamined Patent Publications No. Hei 10-000730 or No. 2002-172735 to an electric apparatus which must employ a light reflector formed into a certain shape for the reasons of the structure or design of the electric apparatus, and a conventional precoated steel sheet for light reflectors of illuminators which was beforehand coated with a white paint was employed.
On the other hand, the problem of generation of heat of an electric apparatus is occurring, with the computerization of electric apparatus, in recent years. As means to solve this heat problem, Japanese Unexamined Patent Publication No. 2002-228085 discloses a technique for improving heat radiative property by making the emissivity of thermal radiation of the inner layer coating film on a metal surface not less than 70 percent.